The present invention relates to the acquisition of data by a digital storage oscilloscope, and more particularly to a method and apparatus for the detection of metastability in triggers that reduces the amount of hardware necessary.
Due to the setup and hold time of latches and flip-flops there is a brief period when there is uncertainty in the transfer of data through such devices. This period is referred to as a metastable region. In a digital oscilloscope such uncertainty in the occurrence of a trigger may result, especially at small time scales on the order of nanoseconds, in a blurring or jitter in the acquired data when displayed. Attempts to eliminate metastability have been hardware intensive, generally requiring the addition of more latches/flip-flops to resolve any uncertainty. One such hardware solution is shown in U.S. Pat. No. 5,004,933, issued Apr. 2, 1991 to Glenn F. Widener entitled "Phase-Selectable Flip-Flop." Such additional hardware adds to the expense of a trigger circuit.
What is desired is a detection of metastability in triggers that eliminates the need for additional hardware while assuring that data affected by trigger metastability is identified.